A/ $\dfrac{4}{7}<\dfrac{5}{7}→\dfrac{4}{7}$ nhỏ hơn $\dfrac{5}{7}$
B/ $\dfrac{12}{21}=\dfrac{4}{7}→\dfrac{4}{7}$ bằng $\dfrac{4}{7}$
C/ $\dfrac{4}{7}=\dfrac{8}{14}>\dfrac{5}{14}→\dfrac{5}{14}$ nhỏ hơn $\dfrac{4}{7}$
D/ $\dfrac{4}{7}=\dfrac{44}{77}$
$\dfrac{9}{11}=\dfrac{63}{77}$
$→\dfrac{9}{11}>\dfrac{4}{7}$
$→\dfrac{9}{11}$ lớn hơn $\dfrac{4}{7}$